/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.servlet.mvc;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import javax.servlet.http.HttpServletRequest;

import org.springframework.lang.Nullable;
import org.springframework.util.StringUtils;
import org.springframework.web.servlet.HandlerMapping;

Simple Controller implementation that transforms the virtual path of a URL into a view name and returns that view. 
Can optionally prepend a prefix and/or append a suffix to build the viewname from the URL filename. 
Find some examples below:

"/index" -> "index"
"/index.html" -> "index"
"/index.html" + prefix "pre_" and suffix "_suf" -> "pre_index_suf"
"/products/view.html" -> "products/view"

Thanks to David Barri for suggesting prefix/suffix support!
Author:
Alef Arendsen, Juergen Hoeller, Rob Harrop
See Also:
setPrefix
setSuffix/**
 * Simple {@code Controller} implementation that transforms the virtual
 * path of a URL into a view name and returns that view.
 *
 * <p>Can optionally prepend a {@link #setPrefix prefix} and/or append a
 * {@link #setSuffix suffix} to build the viewname from the URL filename.
 *
 * <p>Find some examples below:
 * <ol>
 * <li>{@code "/index" -> "index"}</li>
 * <li>{@code "/index.html" -> "index"}</li>
 * <li>{@code "/index.html"} + prefix {@code "pre_"} and suffix {@code "_suf" -> "pre_index_suf"}</li>
 * <li>{@code "/products/view.html" -> "products/view"}</li>
 * </ol>
 *
 * <p>Thanks to David Barri for suggesting prefix/suffix support!
 *
 * @author Alef Arendsen
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @see #setPrefix
 * @see #setSuffix
 */
public class UrlFilenameViewController extends AbstractUrlViewController {

	private String prefix = "";

	private String suffix = "";

	
Request URL path String to view name String. /** Request URL path String to view name String. */
	private final Map<String, String> viewNameCache = new ConcurrentHashMap<>(256);


	
Set the prefix to prepend to the request URL filename
to build a view name.
/**
	 * Set the prefix to prepend to the request URL filename
	 * to build a view name.
	 */
	public void setPrefix(@Nullable String prefix) {
		this.prefix = (prefix != null ? prefix : "");
	}

	
Return the prefix to prepend to the request URL filename.
/**
	 * Return the prefix to prepend to the request URL filename.
	 */
	protected String getPrefix() {
		return this.prefix;
	}

	
Set the suffix to append to the request URL filename
to build a view name.
/**
	 * Set the suffix to append to the request URL filename
	 * to build a view name.
	 */
	public void setSuffix(@Nullable String suffix) {
		this.suffix = (suffix != null ? suffix : "");
	}

	
Return the suffix to append to the request URL filename.
/**
	 * Return the suffix to append to the request URL filename.
	 */
	protected String getSuffix() {
		return this.suffix;
	}


	
Returns view name based on the URL filename,
with prefix/suffix applied when appropriate.
See Also:
extractViewNameFromUrlPath
setPrefix
setSuffix/**
	 * Returns view name based on the URL filename,
	 * with prefix/suffix applied when appropriate.
	 * @see #extractViewNameFromUrlPath
	 * @see #setPrefix
	 * @see #setSuffix
	 */
	@Override
	protected String getViewNameForRequest(HttpServletRequest request) {
		String uri = extractOperableUrl(request);
		return getViewNameForUrlPath(uri);
	}

	
Extract a URL path from the given request,
suitable for view name extraction.
Params:
request – current HTTP request
Returns:
the URL to use for view name extraction/**
	 * Extract a URL path from the given request,
	 * suitable for view name extraction.
	 * @param request current HTTP request
	 * @return the URL to use for view name extraction
	 */
	protected String extractOperableUrl(HttpServletRequest request) {
		String urlPath = (String) request.getAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE);
		if (!StringUtils.hasText(urlPath)) {
			urlPath = getUrlPathHelper().getLookupPathForRequest(request);
		}
		return urlPath;
	}

	
Returns view name based on the URL filename,
with prefix/suffix applied when appropriate.
Params:
uri – the request URI; for example "/index.html"
See Also:
extractViewNameFromUrlPath
postProcessViewName
Returns:
the extracted URI filename; for example "index"/**
	 * Returns view name based on the URL filename,
	 * with prefix/suffix applied when appropriate.
	 * @param uri the request URI; for example {@code "/index.html"}
	 * @return the extracted URI filename; for example {@code "index"}
	 * @see #extractViewNameFromUrlPath
	 * @see #postProcessViewName
	 */
	protected String getViewNameForUrlPath(String uri) {
		String viewName = this.viewNameCache.get(uri);
		if (viewName == null) {
			viewName = extractViewNameFromUrlPath(uri);
			viewName = postProcessViewName(viewName);
			this.viewNameCache.put(uri, viewName);
		}
		return viewName;
	}

	
Extract the URL filename from the given request URI.
Params:
uri – the request URI; for example "/index.html"
Returns:
the extracted URI filename; for example "index"/**
	 * Extract the URL filename from the given request URI.
	 * @param uri the request URI; for example {@code "/index.html"}
	 * @return the extracted URI filename; for example {@code "index"}
	 */
	protected String extractViewNameFromUrlPath(String uri) {
		int start = (uri.charAt(0) == '/' ? 1 : 0);
		int lastIndex = uri.lastIndexOf('.');
		int end = (lastIndex < 0 ? uri.length() : lastIndex);
		return uri.substring(start, end);
	}

	
Build the full view name based on the given view name
as indicated by the URL path.
The default implementation simply applies prefix and suffix.
This can be overridden, for example, to manipulate upper case
/ lower case, etc.
Params:
viewName – the original view name, as indicated by the URL path
See Also:
getPrefix()
getSuffix()
Returns:
the full view name to use/**
	 * Build the full view name based on the given view name
	 * as indicated by the URL path.
	 * <p>The default implementation simply applies prefix and suffix.
	 * This can be overridden, for example, to manipulate upper case
	 * / lower case, etc.
	 * @param viewName the original view name, as indicated by the URL path
	 * @return the full view name to use
	 * @see #getPrefix()
	 * @see #getSuffix()
	 */
	protected String postProcessViewName(String viewName) {
		return getPrefix() + viewName + getSuffix();
	}

}